/Engine/Source/Runtime/SkeletalMeshDescription/Public/SkeletalMeshAttributes.h
this is different from the MeshAttribute::Bone::Name attribute. This is a name of the element that is added to the mesh description to represent Bones (similar to the Vertex/Polygons/Edges elements). MeshAttribute::Bone::Name is just one of the attributes of the Bones element.
static [FName](API\Runtime\Core\UObject\FName) BonesElementName;